EP0576786B1 - Error diffusion processor and method for converting a grey scale pixel image to a binary value pixel image - Google Patents

Error diffusion processor and method for converting a grey scale pixel image to a binary value pixel image Download PDF

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Publication number
EP0576786B1
EP0576786B1 EP93103990A EP93103990A EP0576786B1 EP 0576786 B1 EP0576786 B1 EP 0576786B1 EP 93103990 A EP93103990 A EP 93103990A EP 93103990 A EP93103990 A EP 93103990A EP 0576786 B1 EP0576786 B1 EP 0576786B1
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EP
European Patent Office
Prior art keywords
pixel
value
error
grey scale
scan line
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Expired - Lifetime
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EP93103990A
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German (de)
English (en)
French (fr)
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EP0576786A2 (en
EP0576786A3 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html
Inventor
Arlin R. Jones
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HP Inc
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Hewlett Packard Co
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Publication of EP0576786A3 publication Critical patent/EP0576786A3/xx
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    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T3/00—Geometric image transformations in the plane of the image
    • G06T3/40—Scaling of whole images or parts thereof, e.g. expanding or contracting
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/40—Picture signal circuits
    • H04N1/405—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels
    • H04N1/4051—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels producing a dispersed dots halftone pattern, the dots having substantially the same size
    • H04N1/4052—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels producing a dispersed dots halftone pattern, the dots having substantially the same size by error diffusion, i.e. transferring the binarising error to neighbouring dot decisions

Definitions

  • error value is the difference between the binary pixel value after conversion and the grey scale value of the pixel before conversion.
  • Figs. 4 and 5 illustrate a flow diagram of the procedure employed by the system of Fig. 3.
  • the system of Fig. 3 includes a pair of additional memories which enable rapid accomplishment of the Floyd et al. error diffusion procedure.
  • An error register 44 contains three grey scale pixel error values from the three pixels that have come just before a pixel under consideration.
  • memory positions 46, 48 and 50 contain pixel error values for the first, second and third pixels, respectively, to the left of a pixel under consideration.
  • Figs. 4 and 5 in conjunction with Fig. 3, the procedure followed by the system of Fig. 3 is illustrated.
  • RAM 36 contains an image of grey scale pixels 38.
  • grey scale pixel I i on scan line n is chosen for conversion to a binary value.
  • error register 44 contains previously calculated error values for the three pixels to the left of grey scale value pixel I i on scan line n.
  • the value stored in register position 46 (E i ) is the calculated error value for the pixel immediately to the left of grey scale pixel I i , etc.
  • processor 30 initially causes grey scale value I i to be accessed from RAM 36 (box 60). Before comparing the grey scale value of pixel I i to a threshold value, its grey scale value is modified in accordance with the teachings of Floyd et al. by attribution of fractional grey scale pixel error values from adjacent pixels. As previously indicated, position 46 in error register 44 contains the error value for pixel I i-1 on scan line n. As can be seen from Fig. 2, the fractional attribution of error value to a next succeeding pixel (e.g. I i ) on scan line n is 7/16 times the error value of pixel I i-1 . Thus, as shown in box 62, the error value to be attributed from pixel I i-1 is calculated by multiplying the value E i in error register 44 by 7/16.
  • the preferred method for carrying out the invention is to multiply all grey scale values by 16 and all error values by 16 so as to avoid having to perform fractional arithmetic.
  • Such a multiplication is easily accomplished by a simple shift of the grey scale binary value four-bit positions to the left (or a direct entry of the grey scale value, four positions to the left).
  • each pixel grey scale value on scan line n + 1 will have attributed to it fractions of a pixel error values from pixels on scan line n.
  • pixel 16 on scan line n + 1 will have, as shown, 5/16 of the grey scale error value attributed from pixel P i .
  • pixel P i-1 was considered, 3/16 of its grey scale error value was attributed to pixel 16.
  • pixel 20 (P i+1 ) is considered, 1/16 of its error value will be attributed to pixel 16.
  • attributed error values are found and accumulated for each pixel on scan line n + 1.
  • the corrected grey scale value G i is then compared to a threshold value T (box 68). For a grey scale of 0-255, a threshold value of 127 is assumed (but it may be any other sesired value). If corrected grey scale value G i is greater than or equal to the threshold value, the binary pixel value P i is set equal to the one logical level. If, however, the corrected grey scale value G i for pixel I i is less than the threshold value, then the value of pixel P i is set equal to the 0 logical level. As can now be seen, the binary value of pixel P i reflects not only the grey scale value of pixel I i , but also attributed pixel error values from adjacent pixels. The binary for pixel P i is next stored in page buffer 40 (box 70).
  • the procedure now moves to update the error values in error register 44 in preparation for consideration of pixel I i+1 and so as to enable an attributed error values for pixel positions on scan line n + 1 to be calculated and stored.
  • E i is thus a value that is equal to the corrected grey scale value of pixel I i less the binary value of pixel P i (converted to a grey scale value) (box 72). If pixel P i has a value of One, and the grey scale maximum value is 255, then the grey scale error E i will be equal to the difference between 255 and the corrected grey scale value G i . By contrast, if pixel value P i is set equal to 0, then the grey scale error E i is equal to the corrected grey scale value G i . In either case, E i indicates the difference between the actual binary value of pixel P i and the grey scale value of pixel I i after it has been modified by attribution of error values from adjacent pixels.
  • the contents of error register 44 are shifted one position to the left and the newly calculated value E i is inserted into position 46.
  • the attributed error for a pixel I i-1 on scan line n+1 is calculated and stored in error accumulation buffer 52 (box 76).
  • the value A i-1 is now stored (box 78) in error accumulation buffer 52 and, eventually becomes A i when scan line n+1 is accessed. As previously noted, only a single error accumulation line buffer 52 is required, as the accumulated error for a pixel already considered can be overwritten by a new accumulated error value for a pixel on scan line n + 1.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Image Processing (AREA)
  • Facsimile Image Signal Circuits (AREA)
  • Color, Gradation (AREA)
  • Image Input (AREA)
EP93103990A 1992-07-01 1993-03-11 Error diffusion processor and method for converting a grey scale pixel image to a binary value pixel image Expired - Lifetime EP0576786B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US07/907,006 US5337160A (en) 1992-07-01 1992-07-01 Error diffusion processor and method for converting a grey scale pixel image to a binary value pixel image
US907006 1992-07-01

Publications (3)

Publication Number Publication Date
EP0576786A2 EP0576786A2 (en) 1994-01-05
EP0576786A3 EP0576786A3 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1994-03-02
EP0576786B1 true EP0576786B1 (en) 1997-11-05

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Application Number Title Priority Date Filing Date
EP93103990A Expired - Lifetime EP0576786B1 (en) 1992-07-01 1993-03-11 Error diffusion processor and method for converting a grey scale pixel image to a binary value pixel image

Country Status (4)

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US (1) US5337160A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
EP (1) EP0576786B1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
JP (1) JPH0698159A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
DE (1) DE69315001T2 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)

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US5757516A (en) * 1993-01-11 1998-05-26 Canon Inc. Noise quenching method and apparatus for a colour display system
JP3171993B2 (ja) * 1993-05-24 2001-06-04 キヤノン株式会社 画像処理方法及び装置
US5621542A (en) * 1994-01-20 1997-04-15 Canon Kabushiki Kaisha Image processing apparatus and method with weighting of error data generated in quantization
US5589851A (en) * 1994-03-18 1996-12-31 Ductus Incorporated Multi-level to bi-level raster shape converter
US5692109A (en) * 1994-07-01 1997-11-25 Seiko Epson Corporation Method and apparatus for minimizing artifacts in images produced by error diffusion halftoning
KR0150150B1 (ko) * 1994-07-14 1998-10-15 김광호 에지 강조를 이루는 오차확산 방식 이치화 방법 및 장치
US5739808A (en) * 1994-10-28 1998-04-14 Canon Kabushiki Kaisha Display control method and apparatus
AUPN098895A0 (en) * 1995-02-09 1995-03-09 Canon Kabushiki Kaisha Stable error diffusion
AU710794B2 (en) * 1995-02-09 1999-09-30 Canon Kabushiki Kaisha Stable error diffusion
US6307559B1 (en) 1995-07-13 2001-10-23 International Business Machines Corporation Method and apparatus for color space conversion, clipping, and scaling of an image during blitting
US5892496A (en) * 1995-12-21 1999-04-06 Advanced Micro Devices, Inc. Method and apparatus for displaying grayscale data on a monochrome graphic display
AUPN743096A0 (en) * 1996-01-05 1996-02-01 Canon Kabushiki Kaisha Force field halftoning
US5737453A (en) * 1996-05-17 1998-04-07 Canon Information Systems, Inc. Enhanced error-diffusion method for color or black-and-white reproduction
US5949964A (en) * 1997-06-17 1999-09-07 Hewlett-Packard Company Method and apparatus for halftoning of images in a printer
US6028677A (en) * 1997-09-16 2000-02-22 Hewlett-Packard Co. Method and apparatus for converting a gray level pixel image to a binary level pixel image
US6014227A (en) * 1998-04-30 2000-01-11 Hewlett-Packard Co. Printer with progressive column error diffusion system and method of using same for improved printer throughput
US6179407B1 (en) 1998-11-20 2001-01-30 Hewlett-Packard Company Multi-pass inkjet printer system and method of using same
JP2001128003A (ja) * 1999-10-29 2001-05-11 Matsushita Electric Ind Co Ltd 画像二値化方法
JP2007202170A (ja) * 2000-10-06 2007-08-09 Seiko Epson Corp 画像処理装置、画像処理方法、印刷制御装置、および記録媒体
JP2002185788A (ja) 2000-10-06 2002-06-28 Seiko Epson Corp 画像処理装置、画像処理方法、印刷制御装置、および記録媒体
JP3661624B2 (ja) * 2000-10-06 2005-06-15 セイコーエプソン株式会社 画像処理装置
KR100431000B1 (ko) * 2001-10-23 2004-05-12 삼성전자주식회사 영상블록화현상 보상장치 및 방법
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JP5600517B2 (ja) 2010-08-18 2014-10-01 キヤノン株式会社 情報処理装置、情報処理方法、およびプログラム

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Also Published As

Publication number Publication date
EP0576786A2 (en) 1994-01-05
DE69315001T2 (de) 1998-05-07
DE69315001D1 (de) 1997-12-11
EP0576786A3 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1994-03-02
US5337160A (en) 1994-08-09
JPH0698159A (ja) 1994-04-08

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